1. Field of the Invention
The present invention relates to a gas container valve to be mounted to a gas container for storing a compressed gas or a liquefied gas, and, more particularly to a valve assembly with a check valve for a gas container, provided internally with a check valve so as to prevent degradation of a gas purity, which might be caused when foreign substances such as an air, a rain and the like enter the gas container.
2. Description of the Prior Art
As such a valve assembly with a check valve for a gas container, has been known the one disclosed in U.S. Pat. No. 4,341,245 (Daicho et al.).
The valve assembly disclosed in this patent specification has a gas inlet port and a gas outlet port connected in communication with each other through a gas inlet passage, a gas stop valve chamber, a check valve seat and a check valve chamber in order within a valve box, and a check valve body accommodated within the check valve chamber and resiliently urged to the check valve seat by means of a checking spring so as to be closed. The check valve body has a valve opening pressure differentiating chamber formed in a concaved configuration so as to face the gas outlet port. A check valve body opening member arranged at the leading end of a a gas charging attachment is adapted to be hermetically inserted into the valve opening pressure differentiating chamber through an O-ring, and the cross-sectional area of the hermetically sliding contact portion of the pressure differentiating chamber is larger than the inner cross-sectional area of the valve surface of the check valve body.
This valve assembly with the check valve for the gas container operates as follows.
When a gas is taken out, a gas pressure acting on the valve surface of the check valve body serves to open the check valve body against the valve-closing force of the checking spring. On the other hand, when a residual pressure within the gas container lowers to a predetermined pressure, the valve-closing force of the checking spring overcomes the gas pressure acting on the valve surface and closes the check valve body. In the case that a gas flows reversely from the gas outlet port, a pressure of the reverse-flow gas closes the check valve body interlockingly with the checking spring.
In the case that an empty gas container is recharged with a gas, when the gas charging attachment is coupled to a gas outlet nozzle, the check valve body opening member is hermetically inserted into the valve opening pressure differentiating chamber of the check valve body and the gas is charged under this condition through a gas charging passage of the gas charging attachment. Thereupon, the check valve body is opened by a differential force between the cross-sectional area of the hermetically sliding contact portion of the valve opening pressure differentiating chamber and the inside cross-sectional area of the valve surface of the check valve body on which a charge gas pressure is not acting respectively. When the gas charging attachment is removed from the outlet nozzle after the completion of the gas charging, the check valve body opening member is pulled out from the valve opening pressure differentiating chamber and the check valve body is returned to the valve opening cancellation condition.
The above-mentioned prior art has an advantage of facilitating a gas charging operation because the valve opening and the valve opening cancellation of the check valve body can be carried out simultaneously with the mounting and the demounting of the gas charging attachment relative to the outlet nozzle of the valve assembly, but still has the following drawbacks.
(1) A long time is required for a gas charging.
Since the gas charging attachment is inserted into the narrow gas outlet port having a limited dimension, the cross-sectional area of the gas charging passage in the leading end portion of the attachment can't help becoming narrow. Further, since the check body should have the cross-sectional area of the hermetically sliding contact portion of the valve opening pressure differentiating chamber made larger than the inside cross-sectional area of the valve surface, the external dimension of the check valve body opening member can't help becoming larger. Accordingly, the cross-sectional area of the flow passage provided between the inner circumferential surface of the gas outlet port and the outer circumferential surface of the valve opening member is made narrower.
In this way, since the cross-sectional area of the flow passage is narrow at the time of charging, the time required for a gas charging becomes long. In the case that a gas to be charged is a liquefied gas, this problem becomes remarkable due to a large flow resistance of the gas.
(2) An efficiency of a gas charge working is low.
It is necessary to interpose-a sealing member such as an O-ring and the like between the hermetically sliding contact surface of the valve opening pressure differentiating chamber and the external circumferential surface of the check valve body opening member. In case that the sealing member is damaged by bites of foreign substances such as dirt and dust, the efficiency of the gas charge working is lowered because the charge gas enters the valve opening pressure differentiating chamber to cause a valve opening error.